1. Field of the Invention
This invention relates to a material which enhances the grip on handles of hand-wielded implements such as tennis rackets or baseball bats to increase the coefficient of surface friction between the hand of the user and the handle. This invention also relates to a fabrication method for a grip-enhancing material which produces small surface pores that act as miniature suction cups to grip the hand of the user.
2. Description of Prior Art
In most physical endeavors where a hand-held tool or implement is employed, it is desirable to maintain a sure grip on the handle of the implement. Where the user's hand perspires and the implement is being continuously used, the user is much more prone to lose his grip. This is especially true for implements such as sports rackets which are subjected to intermittent impact forces.
In an attempt to provide a better grip, a group of prior art grip enhancing means has been devoted to the development of molded foam grips manufactured out of plastic or rubber and which contain a large number of small air cells within the material. Sparks (U.S. Pat. No. 3,606,326) discloses a foamed sponge elastomer of the type to be used as a grip for golf clubs and the like. Similarly, Szabo (U.S. Pat. No. 3,813,729) discloses an injection molded foam hand grip for use on a U-shaped suitcase or attache handle. Gavillet (U.S. Pat. No. 3,770,033) discloses a foamed plastic handle for impact tool such as a hammer. The closed cells of this type of grip are created when the grip is formed. Usually this is achieved by forming the grip from a material which is initially soft and moldable. The material is molded into the desired shape and then is solidified, usually by the addition of a catalyst. By addition of the proper chemicals the formation of gas bubbles can be initiated within the material as it solidifies. When the material finally sets, the gas bubbles are incorporated in the material as small closed cells and a "foam" is thereby formed. These prior art grips are shaped using conventional molding techniques and depend upon the compression of the foam by the user's hand to augment the natural surface friction of the grip.
These grips have the disadvantage that they must be specifically molded for the particular implement on which they are to be used. Because the molding equipment is expensive and not readily accessible to the consumer, these types of grips can only be applied to an implement's handle by the original manufacturer of the article. In addition, these types of grips are fairly bulky and are not well suited for application to a handle manufactured for use without a grip enhancing material, without increasing the diameter of the handle unacceptably. Finally this type of grip depends solely upon the surface of the foamed material to create the friction with the user's hand. Occasionally, this may be insufficient to maintain a firm sure grip.
A second type of grip is the foam material which is only used as a grip augmenting cover instead of making up an appreciable bulk of the handle as well. An example of such a grip is disclosed in Meier (U.S. Pat. No. 3,489,031) which is directed to a non-slip foam rubber cover for automobile steering wheels and the like. Another example is disclosed in Kaminstein (U.S. Pat. No. 4,053,676), in which a wax coating is used on a mutli-layered adhesive-backed foam grip cover to reduce slippage.
These cover-like grip enhancing means are also fabricated out of the closed cell foam mentioned above, but because they are thin and flexible they are more readily applied to a handle by the consumer as well as the manufacturer. In addition, application of this type of cover does not significantly alter the diameter of the handle so it may be applied to handles of implements such as tennis rackets where the diameter of the handle is chosen to suit the particular user's hand. A problem with this type of grip enhancing material, is that they too. must depend upon the natural surface friction of the material or upon external coatings for the friction enhancing characteristics of the grip.
Another type of grip designs employ molded rubber suction cups affixed to a flexible sheet which may act as a cover. This type of grip is disclosed in Sweet (U.S. Pat. No. 3,848,871) for a tennis racket handle cover and in Stiller (U.S. Pat. No. 2,466,502) as a sheet with suction cups on both sides to enhance the grip on a bar of soap around which it is wrapped. The problem with this type of grip enhancing device is that it may loosen and fail if the surface to which it is affixed has irregularities or discontinuities. The suction cups of both the above designs may become damaged or deteriorate in time, thereby impairing the suction effect. In addition, size of the suction cups described in both the above designs is such that only a limited number may be in contact with the user's hand at any one time. Therefore, if the suction of one of the cups is lost, the efficacy of the grip is seriously reduced.
A type of open pore friction grip is disclosed in McCracken (U.S. Pat. No. 3,972,528). The grip is permanently applied to a handle by dipping it into a rubber based material which subsequently solidifies to form a thin tacky film. The film bonds directly to the handle and reacts with the user's perspiration to become stickier, thereby enhancing the grip. This grip, however, cannot be readily applied to the handle by a consumer, since it is manufactured from a mixture of materials specifically formulated to bond to the handle of a metal baseball bat. Therefore, this type of grip is not well suited for application to irregular surfaces or non-metallic surfaces.
It is a primary object of the present invention to mitigate the problems of the foregoing grips by providing a thin, flexible, nonabrasive grip cover which may easily be applied by a consumer to the handles of hand wielded implements to improve the characteristics of the grip.
It is another object of the present invention to provide a material which does not use external coatings to enhance its natural surface friction, yet which has enhanced grip characteristics through the utilization of a multiplicity of pores which act as miniature suction cups.
It is yet another object of the present invention to provide a grip, the efficacy of which is enhanced in the presence of water.